1. Field of the Invention
This invention relates to a vertical incinerator for burning general refuses and industrial wastes.
2. Description of the Prior Art
The most usual incinerator known to this day is a stoker type. The stoker type is equipped with a traveling grate adapted to travel in a generally horizontal direction and carry the refuse to be burned thereon. With such a stocker, the refuse is combusted as the grate travels.
However, since the grate of such a stoker travels in a generally horizontal direction, the area of the grate must be very large and, hence, the equipment requires a large installation area. Moreover, this stoker cannot effectively utilize the thermal energy of the hot products of combustion.
To overcome this disadvantage, a vertical incinerator was developed.
The vertical incinerator is mainly a fluidized-bed furnace which is briefly described below referring to FIG. 2.
This refuse pooled in a refuse pit (not shown) is fed to a hopper A by means of a crane (not shown), pulverized by a crusher or a bag breaker B (a machine capable of breaking refuse bags and loosening the blocks of garbage, rubbish and the like), and fed to an incinerating furnace D by means of a feeder C.
The bottom of the incinerating furnace D is provided with an air-jet plate E which carries a pile of high-temperature sand F thereon. As hot air jets for combustion G are blasted against the sand F at high pressure from below the air-jet plate E, the sand F is blown up to form a fluidized bed within the incinerating furnace D. As a commuinuted refuse is fed to this fluidized bed in the furnace D, the refuse is instantly ignited by the fluidized high-temperature sand F and combusted in the so-called free board H in the incinerating furnace D.
The resulting hot products of combustion are withdrawn, together with dust particles, from the top exit I of the furnace D, into an ancillary system communicating with the top exit I, which includes a dust collector and a gas cooler or a heat-exchanger which are not shown.
The heavy non-combusted materials not withdrawn as dust particles are withdrawn downward, together with sand F, into a non-combustibles separator J and the sand F only is returned, by recycling means K, to the incinerating furnace D.
In the above vertical incinerator of the fluidized-bed type, however, a smooth combustion of refuse in the furnace calls for the provision of a crusher or bag breaker for pretreatment and a forced draft fan for fluidizing the sand in the furnace.
Furthermore, since the pressure of the air for combustion to be fed to the furnace must be very high, the conventional incinerator of this type has the drawback of large consumption power.
Moreover, since the amount of the dust discharged along with the hot products of combustion on the dust collector side is very large, the system requires a large-scale dust collector. Moreover, the voluminous dust tends to increase the incidence of troubles in the gas cooler or heat-exchanger system.
In addition, because a high-pressure air for combustion is fed into the furnace, the internal space of the furnace may assume a positive pressure, so that it is not only necessary to seal the refuse feeding port etc. but also necessary to increase the suction force of the induced draft fan used for withdrawing the hot products of combustion and dust from the furnace into the dust collector and other ancillary devices.
It is also essential to provide an additional step and apparatus for circulating the hearth sand.
In addition to the vertical fluidized-bed incinerator described above, there are pyrolysis type and slugging type incinerators as well.
In the incinerator of the pyrolysis type, the pressure of the combustion air to fed into the furnace must be increased to a considerably high level so as to allow the combustion air and hot products of combustion to effectively pass through the thick layer of refuse, with the result that the interior of the furnace may assume a positive pressure due to changes in the quality of refuse to be burned and, as in the case of the fluidized-bed incinerator, the refuse feeding and other ports must be sealed.
Moreover, as the gravity of refuse acts directly on the inside bottom of the furnace, special ingenuity is required in the design and construction of the means for withdrawing the accumulated ashes downward from the furnace bottom, thus adding to the complexity of the equipment.
The incinerator of the slugging type has the disadvantage that because the non-combustibles are withdrawn in high-temperature molten condition, there is a danger in handling.
It is also necessary to employ an additional chemicals. Moreover, the equipment consumes a large electric power. Thus, the slugging type incinerator is costly and economically disadvantageous.